Some 3,200 people crammed Main Street yesterday to rally behind Scott P. Brown, the Republican candidate for U.S. Senate who has built a large following in a short time by threatening to quash the Democratic agenda.

Mechanics Hall was at capacity with 2,200 Brown fans, locals and out-of-staters, who waved signs and flags and cheered for the man they hope will be “the Scott heard round the world.” Overflow crowds were moved to two other locations.

Local celebrities, including former Red Sox pitcher Curt Schilling, former football star Doug Flutie and actor John Ratzenberger, worked the crowd before Mr. Brown took the stage. The state senator from Wrentham, now in the national spotlight, walked to the podium to the tune of The Monkees' “I'm a Believer,” thanked the throng of supporters and told them the finish line is near.

“And we're gonna win!” a man from the audience shouted.

Talk of Mr. Brown's pickup truck, now the subject of jokes from his opponents, did not go away. “I'm Scott Brown, I'm from Wrentham, I drive a truck and I'm asking for your vote,” he said again yesterday.

The Worcester rally was less than 48 hours before voters go to the polls in tomorrow's special election to fill the seat held for decades by the late Edward M. Kennedy. While Brown supporters gathered here, President Barack Obama campaigned with Democratic candidate Martha M. Coakley in Boston.

Mr. Brown had this response to the president's visit: “Democrat or Republican, the president of the United States is always welcome in the commonwealth of Massachusetts.”

While he's here, the president should pull Ms. Coakley aside and remind her about the kind of politics he used to talk about, the politics of conviction, not of negativity, Mr. Brown said.

“Not only are her ads negative, they are malicious. How quickly the politics of hope have been replaced by the politics of desperation,” he said, sparking a “Shame on, Martha!” chant.

Mr. Brown has said he'll be the 41st vote to block the Democratic supermajority in the Senate, while Ms. Coakley wants to be the 60th vote Democrats need to pass major legislation, including health care reform. If Mr. Brown wins, he could block the measure, which is a priority for the president.

The current health care bill, Mr. Brown told supporters, would raise taxes, be unfair to veterans, destroy jobs and run the country deeper into debt. “As your senator, I will insist that they start over,” he said.

He supports the troop increase in Afghanistan and said he, unlike Ms. Coakley, would work to defend the United States from terrorists in that country and others.

“Our tax dollars should pay for the weapons to stop them, not the lawyers to defend them,” he added. Ms. Coakley has said suspected terrorists should be tried in civilian court while Mr. Brown supports the military tribunal process, which has different rules.

Mr. Brown spent much of the day in Central Massachusetts, with stops at the Kenmore Diner and his campaign headquarters in Worcester, followed by a quick rally at Wachusett Mountain Ski Area in Princeton. He was mobbed by supporters at Mount Wachusett, who pushed through the crowd to shake his hand, snap a photo or get his autograph.

The candidate told the Telegram & Gazette that nothing could be done to the current health care bill that would move him to vote for it. “No, there's been so much behind closed doors,” he said.

Former Republican governor Paul Cellucci came out to support Mr. Brown yesterday, telling the Mount Wachusett crowd, “On Tuesday, we're going to send a shock wave to Washington, D.C.”

Mr. Brown has said the seat he's running for is not the Kennedy seat or the Democrat seat, it's the people's seat. But many of his supporters as well as Ms. Coakley's supporters are surprised the race is so close in a state that has elected only Democrats to Congress for years.

“Out of nowhere, there's all this momentum. It's incredible,” said Jeff Ruscitti of Marlboro, a Brown supporter who came to Mechanics Hall.

Another supporter, James M. Perry of Norton, said a Brown victory would be a “Massachusetts miracle.”

“This can happen,” he said. “If it happens, it'll be a wake-up call to the rest of the nation.”

This is one of the closest races Marilyn I. Harris has seen in her many years of voting. She's voting for Mr. Brown because she believes the big government favored by Democrats is taking freedoms away from people. “We have a chance here to begin to change the tide,” the Shrewsbury woman said.

In his plug for Mr. Brown, Mr. Schilling, the retired Red Sox pitcher who helped his team win two world championships, compared the campaign to the Red Sox's come-from-behind victory in 2004. “This feels like the clubhouse on the morning of Game 7 of the (American League Championship Series),” he said.

He also cleared up one thing: “I am not a Yankee fan,” he said.

Ms. Coakley, the state's attorney general, recently said Mr. Schilling was a Yankee fan. Interviewed by reporters after the rally, Mr. Schilling said personally, he doesn't care much about the comment, but it reflects on Ms. Coakley's relationship with her constituents. “She's very out of touch with the people,” he said.

The Coakley campaign was also in Worcester yesterday, with U.S. Sen. John F. Kerry and other Democrats leading a rally in Lincoln Square in the morning. Many of the attorney general's supporters gathered across the street from the Brown campaign rally at Mechanics Hall in the afternoon.

Alec Loftus, a Democratic Party spokesman in Worcester yesterday, said Mr. Brown artificially inflated his ranks by busing loads of out-of-state Tea Party activists to Mechanics Hall. The Lincoln Square rally for Ms. Coakley, however, was attended by Massachusetts residents only, he said.

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